| In the whole breeding industry chain of Litopenaeus vannamei,the germplasm problem is the primary problem restricting the stable development of the industry of Litopenaeus vannamei in China,and great germplasm is one of the important guarantee to promote the quality and efficiency of prawn industry.In addition,improved germplasm also requires improved methods,and breeding management,especially water quality management,which is also very important.The utilization of probiotics to stabilize the environment of aquaculture water,construction of bacteria regulation system,and optimization of ecosystem of shrimp breeding are also important research contents for industry chain of shrimp breeding.This paper aims at the key problems of "improved germplasm" and "improved aquaculture methods" existing in industry chain of shrimp breeding in Fujian province.On the one hand,the molecular germplasm identification and analysis technology which is based on microsatellite technology was constructed to analyze the genetic structure of germplasm and genetic diversity level of Litopenaeus vannamei in Liuwudian,xiamen,which is the main origin area of shrimp seeding in Fujian province,in order to understand the present situation of germplasm of shrimp seeding production in Fujian province.On the other hand,the paper analyzes and innovates the regulation technology of water quality of the characteristic aquaculture mode-the mixed pond aquaculture mode-of shrimp breeding in Fujian province.At the same time,the initial Bacillus which can effectively degrade the ammonia nitrogen in the water was screened out from the shrimp pond,and the production fermentation formula was optimized and the production formula with low cost and high yield was developed,which provided an important technical guarantee for the water quality regulation of shrimp ponds.The main results are summarized as follows:1.Analysis for genetic diversity of broodstock populations of breeding Litopenaeus vannamei.Eight pairs of primers are selected to analyze the genetic diversity of five random broodstock populations(ZhaoAnl?HaiNan?ZhaoAn2?ZhangPu?DongShan)of Litopenaeus vannamei by using microsatellite labeling technology.The results indicate that a total of seventy-five alleles(Na=75)are detected in eight pairs of primers in five populations,with average numbers of alleles(Na=3.875?7.000),average effective numbers of alleles(Ne=2.632-3.719)and average polymorphism information content(P/C=0.498?0.624).The average observed heterozygosity(Ho)is 0.410 to 0.562 and the average expected heterozygosity(He)is 0.589 to 0.687.The average number of inbreeding lines(Fis)of each population is 0.147-0.305,indicating a high degree of inbreeding in each population and the absence of heterozygotes.Except population ZP and DS,other groups deviate from equilibrium significantly at multiple microsatellite sites(P<0.05),which indicate that most groups have phenomenon of heterozygote deficiency.Genetic variation analysis results show that the genetic differentiation index(Fst)is 0.028-0.199.According to Fst calculation,the genetic distance of Slatkin's is between 0.029 and 0.249.The results of this study show that there are a different level of inbreeding phenomenon in the five broodstock populations of Litopenaeus vannamei.In this research,the genetic diversity of five broodstock populations of Litopenaeus vannamei in xiamen is analyzed in order to clarify genetic structure,germplasm resources and inbreeding degree of broodstock populations of Litopenaeus vannamei in Xiamen and provide background information and suggestions for purification,optimal protection,rejuvenation and genetic breeding of germplasm resources of Litopenaeus vannamei for this area.2.Effects of adding probiotics and compound nutrients for water quality and community structure of bacterial in fish-shrimp mix-culturing pond Aquaculture environment was regulated by adding probiotics and compound nutrients to fish-shrimp mix-culturing pond,and evaluate the effect of regulation of water quality.Illumina HiSeq2500 sequencing platform was used to 16S rDNA sequencing for bacterial diversity in aquaculture to obtain the bacterial composition and abundance.The result of water quality test show that the range of parameters such as transparency,pH,dissolved oxygen(DO),ammonia nitrogen(NH3-N)and nitrite(N02-N)is within the appropriate range and the concentration of harmful vibrio is far lower than pathogenic concentration under the regulation,which indicates that the method can maintain stable of water environment and inhibit the reproduction of pathogenic bacteria.The result of bacterial community composition and abundance analysis showed that the number of OTU in aquaculture was 1878,among which the number of OTU in boundary,phylum,class,order,family,genus and species was 4,43,79,91,652,952 and 16,respectively.The relative abundance of bacteria in aquaculture was mainly dominated by Cyanobacteria,Proteobacteria,Actinobacteria,Bacteroidetes and Firmicutes,accounting for 38.19%,28.11%,18.85%,12.85%and 0.08%of the total bacteria,respectively.The result indicates that the diversity of bacterial community in fish-shrimp mix-culturing pond was higher after the addition of probiotics and compound nutrients,which contained many common probiotics in aquaculture.This study provides a theoretical basis for improving the ecological environment of aquaculture and healthy breeding of fish and shrimp.-3.Isolation and identification of a strain of Bacillus that can degrade ammonia nitrogen from breeding water of shrimp(Litopenaeus vannamei)and optimization of its fermentation formulaIn this experiment,Bacillus with the degradation effect of ammonia nitrogen,including free ammonia(NH3-N)and ammonium salt(NH4+),was isolated and screened from breeding outdoor pond of shrimp(Litopenaeus vannamei)under(28±1)°C.The single factor experiment was used to optimize the fermentation formula of the screened Bacillus and select the low cost and high yield fermentation medium formula.The results of strain isolation and screening and ammonia nitrogen degradation experiment showed that:after preliminary isolation,five strains of Bacillus(DS1,DS2,DS3,DS4 and DS5)were obtained,and then one strain of Bacillus DS5 that could significantly degrade ammonia nitrogen in water was obtained through ammonia nitrogen degradation experiment.Within five day,the DS5 strain rapidly degraded the ammonia nitrogen in water,reaching the maximum degradation rate(36.41±0.07)%on the fourth day,and the ammonia nitrogen in the last 3 day water remained stable at about 36%.The strain DS5 was preliminarily identified as Bacillus subtilis by 16S rDNA sequence analysis,morphological,physiological and biochemical identification.Fermentation formula experimental results of strain DS5 show that under 28 0C,when carbon source adding 59‰ glucose,nitrogen source added 109‰ soybean meal and inorganic salt adding 5‰?sodium chloride,strain grew well,the number of bacteria in culture medium was higher.To consider the cost and the amount of bacteria,5‰ glucose,10‰ soybean meal,5‰sodium chloride was selected as the optimum fermentation medium for this strain. |
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